A Heating, Ventilating and Air Conditioning (HVAC) Control Valve is essential in maintaining one’s home temperature. It can control the flow of fluid as it is used for varying the size of the passage which is being managed by a signal controller. For that, it is also called the “final control element”.
HVAC control valve take care of the liquid or gas flow by means of opening or closing the internal passages. There is a shift in the valve stem which gives way to an increased, decreased or steady flow in the passage. The control valve opens when the setpoint does not match the process parameter.
The components of the HVAC control valve includes the valve, the actuator, and the controller.
One type of valve is the plug design. The system of that design involves the plug being closed and is against the seat. The second type is the seat design. For that, the system is that the valve is a quarter-turned disc or ball that is against the seat.
The actuator is used for moving the valve stem
The controller then calculates the change’s size to the internal passage and thus determines the desired rate of the flow. Air or electricity is usually what drives the controller.
The difference in the pressure between the inlet and outlet is the deciding factor in the rate of the flow. The valve closes when the flow needs to slow down which gives way for more back-pressure and a bigger difference in the inlet and outlet pressure. The valve then opens when the flow needs to increase, in turn, it reduces the back-pressure and the inlet and outlet pressure difference.
What regulates the flow in the control valve is the valve trim. To control the flow, the trim can conjure passages or different shapes and sizes. The trim is made up of a fixed-in-place seat as well as a movable cone, disc, ball, or plug.
With regard to the process parameters, the controller is what determines the response of the valve. When there is a detection for the need for correction, the control valve’s tuning is the one that controls the response’s intensity and speed.
To produce an output for the actuator, the controller’s process involves:
- the discrepancy of the size between the current value and the set point of the controlled parameter
- the discrepancy in the length of time
- the discrepancy in speed
Then, it calculates the speed and distance of the stem.
Do take note that measuring your pipeline is important as it is what determines the size of the control valve you are looking for. And make sure that the control valve is packed in perfect condition for some problems that may arise otherwise.